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At what point does the boundary between a high-altitude skydiving suit and re-entry spacecraft become blurred? With the right definitions someone could say that

by jchook 12y ago

At what point does the boundary between a high-altitude skydiving suit and re-entry spacecraft become blurred? With the right definitions someone could say that Yuri Gagarin has this record beat.

ars 12y ago
With reentry you are in orbit first (i.e. velocity tangent to the ground). With a free fall you are at standstill relative to the ground before you start.
- deleted 12y ago
  [deleted]
- pmontra 12y ago
  Maybe I'm being pedantic but it's possible to perform a reentry without being in orbit first. Most notable cases, the Apollo missions. They plunged directly into the atmosphere without entering orbit. Details and rationale at http://boards.straightdope.com/sdmb/showthread.php?t=607491 http://boards.straightdope.com/sdmb/showthread.php?t=607491
  - ghshephard 12y ago
    The Apollo was either on the moon or orbiting the moon, so in either case it was orbiting the earth.
    - pmontra 12y ago
      A very peculiar orbit but OK. So my next candidate is the Startdust mission. That went into a solar orbit and released a capsule to return samples to Earth on a fly by in 2006 before being sent to visit a comet in 2011. That capsule is quoted to have been the fastest reentry for a man made object at 12.9 km/s, which is faster than Earth escape velocity at sea level. http://en.wikipedia.org/wiki/Stardust_%28spacecraft%29#Launch_and_trajectory http://en.wikipedia.org/wiki/Stardust_%28spacecraft%29#Launc...
- shkkmo 12y ago
  Re-entry is just re-entering the atmosphere. The use of atmospheric braking is a common, but not required, part of atmospheric re-entry. It is theoretically possible, if highly inefficient, to lose orbital velocity by using propulsion and re-enter from orbit without using atmospheric braking. To answer the original question, re-entry occurs when the atmosphere is first left and then re-entered. The definition of where this boundaries lies is ambiguous, but most definitions put it in the 80-120km range. So Alan reached 1/2 to 1/3 of the elevation that would have been required for this to qualify as re-entry.

by jchook 12y ago

At what point does the boundary between a high-altitude skydiving suit and re-entry spacecraft become blurred? With the right definitions someone could say that Yuri Gagarin has this record beat.

ars 12y ago

With reentry you are in orbit first (i.e. velocity tangent to the ground). With a free fall you are at standstill relative to the ground before you start.

deleted 12y ago
[deleted]
pmontra 12y ago
Maybe I'm being pedantic but it's possible to perform a reentry without being in orbit first. Most notable cases, the Apollo missions. They plunged directly into the atmosphere without entering orbit. Details and rationale at http://boards.straightdope.com/sdmb/showthread.php?t=607491 http://boards.straightdope.com/sdmb/showthread.php?t=607491
- ghshephard 12y ago
  The Apollo was either on the moon or orbiting the moon, so in either case it was orbiting the earth.
  - pmontra 12y ago
    A very peculiar orbit but OK. So my next candidate is the Startdust mission. That went into a solar orbit and released a capsule to return samples to Earth on a fly by in 2006 before being sent to visit a comet in 2011. That capsule is quoted to have been the fastest reentry for a man made object at 12.9 km/s, which is faster than Earth escape velocity at sea level. http://en.wikipedia.org/wiki/Stardust_%28spacecraft%29#Launch_and_trajectory http://en.wikipedia.org/wiki/Stardust_%28spacecraft%29#Launc...
shkkmo 12y ago
Re-entry is just re-entering the atmosphere. The use of atmospheric braking is a common, but not required, part of atmospheric re-entry. It is theoretically possible, if highly inefficient, to lose orbital velocity by using propulsion and re-enter from orbit without using atmospheric braking. To answer the original question, re-entry occurs when the atmosphere is first left and then re-entered. The definition of where this boundaries lies is ambiguous, but most definitions put it in the 80-120km range. So Alan reached 1/2 to 1/3 of the elevation that would have been required for this to qualify as re-entry.